LaBa2Cu3O8−y, pérovskite de cuivre à valence mixte déficitaire en oxygène supraconductrice en dessous de 75 K

LaBa 2 Cu 3 O −y , mixed valence copper perovskite, oxygen deficient and superconductive below 75 K. A novel mixed valence copper oxide LaBa 2 Cu 3 O 8−y , oxygen deficient perovskite, has been isolated. This tetragonal compound (a=3.91 A, c=11.74 A), is isostructural with the superconductive pseudo-tetragonal oxide YBa 2 Cu 3 O 8−y previously described [1]. This oxide which is metallic at high temperature (e=2.4×10 −3 Ω•cm at 293 K) exhibits a narrow resistive transition at 75 K: below this temperature it reaches a zero resistance. Rather high current densities (d=10 A/cm 2 ) can be applied to this compound without changing its superconductive character at 70 K. A structural model is proposed for this oxide, and is compared to the structure of the oxygen deficient perovskite La 3 Ba 3 Cu 6 O 14+ [2] Le compose cristallise dans le systeme quadratique et est isostructural de YBa 2 Cu 3 O 8−y pseudoquadratique. Semi-metallique a haute temperature, il presente une transition resistive etroite a 75 K, temperature en dessous de laquelle il atteint une resistance nulle